Process for manufacturing rayon having high degree of polymerization by the viscose process



INVENTOR AJ'AEDA ATTORNEYS T/IKASH/ W/IHOUT 779679 r/Mwr or #707 A 00 8A 71/ I05 DAYS TAKASHI ASAEDA TRfATfO WITH/107 (QC/0 84 TH OF POLYMERIZATION BY THE .VISCOSE PROCESS original Filed Sept. 11, 1965 PROCESS FOR MANUFACTURING RAYON HAVING HIGH DEGREE A ril 14, 1970 M312 g/vs cA-ZluoSE United States Patent 3,506,754 PROCESS FOR MANUFACTURING RAYON HAV- ING HIGH DEGREE OF POLYMERIZATION BY THE VISCOSE PROCESS Takashi Asaeda, Kuse-gun, Japan, assignor to Tachikawa JResearch Institute, Kyoto, Japan, a corporation of apan Continuation of application Ser. No. 308,137, Sept. 11, 1063. This application Sept. 27, 1967, Ser. No. 671,545 Int. Cl. D01f 3/12 US. Cl. 264-191 2 Claims ABSTRACT OF THE DISCLOSURE The application discloses a method of making high DP rayon by the viscose process. The method includes a xanthation step prior to which the CS and the surfactant are mixed together. After xanthation the resulting viscose is heated to within C. of the spinning bath temperature. A hot bath follows the spinning bath. A tapered godet stretches the spun filaments between the godet in combination with a second godet having a maximum of one step over which the filaments are drawn. The second godet may be either in or out of the spinning bath.

This is a continuation of Ser. No. 308,137, filed Sept. 11, 1963.

This invention relates to improvement of the process for producing rayon filaments or fibers having a high degree of polymerization (DP i.e. more than 500, by means of the viscose process. Until now, there have been many inventions for the production of rayon filaments or fibers with high DP by viscose process such as are disclosed, for example, in US. Patents Nos. 2,607,- 955; 2,703,270; 2,705,184 and 2,732,279. However, the present inventors have found that in order to get filaments or fibers with more than 500 DP by the viscose process, all processes known hitherto have some defects from the commercial point of viewsuch defects, for example as low spinning velocity, low capacity of the spinning machine, complicated spinning operation, critical control of manufacturing conditions etc., and it is universally understood that the practical upper limit of DP of the product would be 500, this being especially true if it is desired to have substantially the same spinning capacity of the spinning machine as with ordinary viscose rayon staple of low DP, the DP of such staple being considerably below 500. On the other hand, cellulose chemistry teaches us that in order to get improved qualities of filaments or fibers from the viscose process, high DP staple should be used and treated. According to the present invention there is provided a viscose process which treats high DP staple, but which does not possess the limitations described above.

The following are the details of the description of the present invention. The first essential condition of the invention is the xanthation of alkali-cellulose with CS containing 0.23.0% surfactants. The advantages of this xanthation-procedure lie not only in the acquiring of high DP-cellulose xanthate of highly uniform quality and good filterability, but also in the facilitating of the heating of the viscose as described in the next paragraph. Although for such' surfactants, either anionic, cationic or nonionic compounds can be used, the important condition is to use such surfactants as to effect a good balance between the CS and the alkali in the alkali-cellulose. For example, for an anionic compound about 40% sulphonated ricinolein should be used for a cationic compound, addition-compounds of alkylamine or alkylamide with ethylene oxide may be employed, and

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for a nonionic compound addition-compounds of higher alcohol with ethylene oxide may be used. By such Xanthation, it is very easy to get a clear viscose having a viscosity more than 300 by the falling ball test.

The second essential condition of the invention is to specify the temperature of viscose during spinning. Generally speaking, for the spinning of viscose with high DP. the 'y-value of the viscose should be high enough, and consequently the degree of ripening of viscose is preferably low, and for such purpose, it is intended to keep the temperature of the viscose below 15 C. before spinning. However, as the temperature of the spinning bath of the present invention is more than 25 0., there is a temperature difference of more than 10 C. between the viscose and the spinning bath. Such difference hinders smooth spinning procedure of high DP viscose. In the present invention, by warming up the viscose near the spinneret, the temperature difference between the viscose and the spinning bath shall be adjusted to below 10 C., and preferably to 5 C. At the same time, the viscose obtained by the xanthation step described above can completely obviate the disadvantages derived from heating the viscose. Thus, it is possible to improve the spinnability of viscose, without any influence on the ripening of the viscose, and to increase the uniformity of quality of the final product. Moreover, to heat spun viscose is to make its viscosity lower, especially with high viscosityviscose, and we have been able to treat easily high viscosity-viscose for spinning which has been difficult hitherto.

The third essential condition of the invention is to apply an utterly new spinning system for spinning the viscose produced by the procedures mentioned above. As generally accepted, the process of the formation of rayon filaments or fibers by the viscose process is composed of three stepscoagulation, regeneration and recrystallization of cellulose, and at a suitable time during the spinning, the filaments are to be stretched by external force. Naturally, these steps are not independent of each other, rather they are quite dependent. The present spinning system has resulted from the study of such points. The spinning bath whose concentration of sulphuric acid is less than 30 g./l., contains 0.1-2.0 g./l. of one of the sulphates of the heavy metalse.g. Zn, Co, Ni, Cr, Cd etc. and is heated to a temperature of more than 25 C. In the spinning baths shown in the examples illustrated in FIGURES l-3, the spinning velocity of the spun thread is being increased gradually and in balance with coagulation, regeneration and recrystallization of the cellulose.

In the drawings:

FIGURE 1 shows applicants spinning bath with a. two step godet inside the bath;

FIGURE 2 shows a spinning bath with a single step godet inside the bath;

FIGURE 3 shows a spinning bath with a combination single step and two step godets outside the bath;

FIGURE 4 is a graph illustrating the amount of iodine absorbed by the filaments with and without the hot acid bath.

Referring to the FIGURE 1 and FIGURE 2 of the drawings it is seen that the xanthogenate is first passed through viscose heater 8 into the spinning bath 1 wherein it is extruded from spinneret 2. The coagulating filaments travel through thread guide 4 to a small godet 3 within the bath. In FIGURE 1 the godet is a two step device while in FIGURE 2 the godet within the bath is a single step, cylindrical element. The filaments then pass over guide 4 and out of the bath to a special combination, cylindrical and conical godet 6 from which it passes over guide 4' to a hot acid bath 7.

In FIGURE 3 the godet 3' and guide 4 are outside the bath, there being only a fixed thread guide 5 disposed within the bath in advance of the spinneret.

Applying such spinning devices illustrated in drawings, the adjustment is very easy to get a suitable correlation, of coagulation, regeneration and recrystallization of cellulose after spinning, and consequently, the characteristics of final products are far better than those produced by previous processes, e.g. that disclosed in Patent No. 2,732,279. See Table B below. In Patent No. 2,732,- 279, it is proposed to stretch thread on the conical or stepped godet immersed in the spinning bath corresponding to coagulation and regeneration, but it seems a little difficult to stretch equally many numbers of filaments at the same time on the godet on account of its mechanism, and therefore, it has such defect as not to permit an increase in the spinning capacity of the spinning machine as is commercially required from industrial point of view, and there is imposed an upper limit in the spinning speed because of the complexity of its operation. On the other hand, in the present system, all of such defects have been completely remedied by a new spinning procedure, and the industrial disadvantage of spinning viscose filaments or fibers having a high DP as mentioned previously have been completely overcome. Therefore, the spinning capacity per unit length of the spinning machine for high DP-viscose becomes nearly equal to that for ordinary viscose of low DP. It should be noticed that any stretching device similar to those shown in the drawings comes into the scope of the present invention, as far as it is able to perform equivalently according to the principle of the present invention.

On the other hand, I have found some special phenomena which may occur at times in using the present spinning system. One of these phenomena is that some delay of recrystallization of the cellulose in filaments form may occur owing to insufiicient neutrallization during passage in the spinning bath, and it comes from low acid concentration of the spinning bath and relatively high spinning speed. The other phenomenon concerns the problem of controlling the quality of the filaments or fibers produced by the present spinning system owing to the delay of recrystallization. For example, it has been recognized that the fibers become unstable when they are subjected directly after the spinning to an ordinary washing operation involving desulphurising and bleaching, or sometimes, even if satisfactory fibers are obtained after the final step in the process, due to the lapse of time, some change in the inner structure of the fibers causes a degradation in the quality.

According to the inventors research, in order to prevent fibers from such defects, it is well not to treat the spun filaments to stretching after spinning in a hot bath containing less than g./l. sulphuric acid and having a bath temperature of more than 80 C. Hitherto, it has been generally accepted that the hot acid bath or neutral bath should be used for the passage of ordinary rayon filaments with low DP after spinning in order to improve their quality. Such procedure usually requires that the filaments be subjected in the hot bath to a positive stretching in order to increase tenacity without loss of elongation. On the contrary, in the present system, subjecting filaments to positive stretching is avoided. The purpose of using a hot bath in the present system is to remove any distortion in the inner fibral structure produced during spinning, and also to increase the degree of recrystallization of cellulose to such a degree as not to permit a degradation in quality to occur during the Washing operation. Thus, the effect of the hot acid bath in the present system is utterly different from the previous ones ordinarily used in rayon staple of low DP, and in order to achieve its desired effect, attention should be paid to the duration or the length of the passage of filaments in the hot bath, e.g. when 60,000 deniers tow is treated, in the bath with 3 g./l. sulphuric acid, at 85 C. with a speed of 30 m./min., the minimum length of the passage shall be 2 meters. The provision of a hot acid discovered from use of the present process.

TABLE (A) Number of Example 1 2 3 4 5 6 7 Spinning temperature a0 30 32' 35 44 25 40 C0no.ofZnSO4(g./l.) .0.35 0.10 0.20 0.5 2.0 0.3 1.0

(CdSO-l) The degree of recrystallization during the spinning procedure can correspond approximately to the primary swelling of filaments which can be measured by the ratio of the water content in the filaments to its bone dry weight, and the change of the inner structure of filaments at the elapsed time can be determined by the change of the absorption of iodine by filaments.

EXAMPLE 1 Wood pulp with DP 900 is immersed in 18.5% NaOH solution for 2 hrs. at 20 C., pressed to 2.8 times of its weight, crushed for 1 hr. at 20 C. Alkali-cellulose thus obtained is xanthated with the mixture of 45% CS (to cellulose) and 0.2% laurylalcoholethylene oxide at 19 27 C., and the composition of viscose is 5% cellulose and 3% NaOH. The viscosity by falling ball test and the gamma value at the spinning is 440 and 67 respectively. Viscose is warmed just before the spinning machine at 26 C. The spinning bath to be used contains H 15.5 g./l., ZnSO 0.35 g./l., Na SO 60 g./l. and its temperature 30 C. Filaments are stretched by the system as shown in FIGURE 1, the spinning speed being 20 m./min. 60,000 denier tow passes through the bath containing H SO 3 g./l. at C. for 12 sec. Filament characteristics obtained are shown in data line 1A of Table B. Data of 1B of table show-s filament characteristics which are not subjected to a hot bath treatment.

EXAMPLE 2 Alkali-cellulose is obtained from wood pulp with DP 950 by the same conditions as in Example 1, and the xanthation is also taken place in the same way as in Example 1 with 48% CS and 3% of 40%-sulphonated ricinolein. The composition of the viscose is 5% cellulose and 3% NaOH. The viscosity is 450, 'y-value is 70 at the spinning. Viscose is warmed to 26 C., and is spun according to the same condition as in Example 1, but with ZnSO 0.1 g./l. and Na SO 8O g./l., and the system shown in FIGURE 2. 30,000 denier tow thus spun is treated in the hot bath with H SO 5 g./l. at C., the length of immersion being 3 meters, and the spinning velocity is 25 m./ min. Filament characteristics are shown in Table B, line 2. The primary swelling of the filaments is 650 before and 205 after the hot bath.

EXAMPLE 3 Wood pulp with DP 1150 is immersed in 18.8% NaOH solution for 2 hrs. at 20 C., pressed to 2.8 times, crushed for 2 hrs. at 20 C. The xanthation is done with the mixture of 50% CS and 0.5% lauryl alcohol-ethylene oxide at 19-27 C., and the composition of viscose is 5% cellulose and 3.3% NaOH, viscosity is 560, 'y-value is 75 at the spinning. Viscose is warmed at 25 C., and is spun at 32 C. by H 50 16.0 g./l., ZnSO, 0.2 g./l., Na SO 80 g./ 1., and the system shown in FIGURE 3. Filaments pass through the bath with H SO 3 g./l. at 90 C. Table B line 3 shows the filament characteristics obtained. FIG- URE 4 shows the change of absorbed iodine in filaments treated with and without the hot bath.

5 EXAMPLE 4 Linter pulp with DP 1300 is immersed in 19.2% NaOH solution at 20 C. for 2 hrs., pressed to 2.86 times,

Needless to say, these examples are illustrated as examples of the present invention, and are not restrictive thereof.

TABLE (B) Tenacity (g. Id.) Elongation (percent) Knot tenacity Hot Denier Dry Wet Dry Wet (g./d.) DP bath Filament characteristics obtained according to the process disclosed in Patent No. 2,732,279.

crushed at 25 C. for 1.5 hrs. The xanthation is done with the mixture of 60% CS and 1% polyoxyethylenealkylaminoether at 30 C. The composition of viscose is 4.5% cellulose and 3.6% NaOH, and viscosity is 560, 'y-value is 78 at the spimiing. Viscose is warmed at 32 C. just before the spinning, and is spun in the bath with H SO 13.3 g./l., ZnSO 0.5 g./l., Na SO 40 g./l. at 35 C. according to the system shown in FIG- URE 3. In this example, the comparison of characteristics of tows of 30,000 deniers of 4 rn. and 2 m. lengths which pass through the hot bath with H 80 3 g./l. at 90 C. is shown in Table B, lines 4A and 4B, respectively.

EXAMPLE 5 The viscose prepared as in Example 2 is heated to 35 C. before the spinning, is spun in the bath containing H 50 13.8 g./l., ZnSO 2.0 g./l. at 44 C. according to the system shown in FIGURE 3. The filaments pass through the hot bath with H SO 8 g./l. with 40 m./min. speed. Characteristics of filaments are shown in Table B, line 5.

EXAMPLE 6 Viscose prepared in the same manner as in Example 4 is heated to 23 C., and is spun in the spinning bath containing H 50 15.2 g./l., CdSO 0.3 g./l. at 25 C. according to the system shown in FIGURE 2. Spun filaments pass through in the hot bath of 90 C. with H 50 5 g./l. at the speed of 20 m./min. Characteristics of filaments are shown in Table B, line 6.

EXAMPLE 7 Viscose is prepared by the same way as in Example 4 except the temperature of xanthation is 1929 C. Viscose obtained has the viscosity 620, 'y-value 77. After the viscose is heated to 40 C., it is spun in the bath containing H 80 29.3 g./l., ZnSO 1.9 g./l. at 49 C. for the purpose of producing carpet-fibers of 15 deniers. Filaments pass through the bath with H 80 9 g./l. at 90 C., and are treated according to the usual Washing procedures. The fiber characteristics obtained are shown in Table B, line 7.

What is claimed is:

1. In a process for producing rayon filaments the steps of mixing CS with .2-3.09% surfactant prior to xanthation, said surfactant being an anionic, cationic or nonionic compound and employing the mixture to xanthate alkali-cellulose, heating the resulting viscose to within 10 C. of the spinning bath temperature and spinning the viscose in a bath which is higher than 25 C. and which contains sulphuric acid of less than 30 gr./l. and 0.1-2.0 g./l. of one of the sulphates of heavy metals selected from a group consisting of Zn, Co, Cd, Ni and Cr, the filament gels being then passed in relaxed state through a hot bath containing H of less than 10 gr./l. at a temperature higher than 80 C. in order to fix completely the inner structure of the cellulose, the filaments being stretched between said spinning bath and said hot bath.

2. In a process as defined in claim 1, wherein the filaments are stretched 'by passing the filaments over a single step godet and over a second godet which is conical in shape causing the spinning velocity of the spun filaments to increase gradually with the coagulation regeneration and recrystallization of the cellulose.

References Cited UNITED STATES PATENTS 2,439,829 4/1948 Tippetts 264 X 2,611,928 9/1952 Merion et al 264-197 2,732,279 1/1956 Tachikawa 264-198 2,775,505 12/1956 'Pedlow 264-181 2,946,650 7/1960 Tachikawa 264-197 X 2,946,782 7/1960 Tachikawa 260217 3,046,085 7/1962 Burroughs et al. 3,108,849 10/1963 Owashi et al. 3,139,467 7/1964 Drisch et al. 3,182,107 5/1965 Howsman et al. 264-191 X FOREIGN PATENTS 827,415 2/1960 Great Britain.

DONALD J. ARNOLD, Primary Examiner I. H. WOO, Assistant Examiner US. Cl. X.R. 264188 

